In humans, as in most animal cells, genetic information is housed not only in the nucleus, but also in mitochondria (see Figure 1). Mitochondrial DNA (mtDNA) encodes thirteen essential proteins of the oxidative phosphorylation complexes as well as 22 tRNAs and 2 rRNAs required to translate these thirteen mRNAs in the mitochondrial matrix. Mutations in mtDNA cause maternally inherited neuromuscular disorders due to declines in cellular energy metabolism. In addition, mtDNA mutations accumulate in normal aging tissues, certain tumors, and have been implicated in late-onset diseases such a Alzheimer's, Parkinson's, and diabetes, indicating that the pathology of dysfunctional mitochondria is only beginning to be unraveled. The research in my laboratory is directed toward understanding the mechanism of gene expression in human mitochondria and its impact on human aging and disease. The ultimate goal is to understand the full impact of dysfunctional mitochondrial gene expression on human health and use this information to design specific interventions to treat mitochondria-based disease and age-related pathology.
Specifically, we focus on nucleus-encoded factors that are imported into the organelle to regulate transcription, translation, replication, and maintenance of mtDNA. We are also concerned with signaling pathways that connect the nuclear and mitochondrial genomes to coordinate gene expession patterns in both compartments. We use multiple approaches to this problem including the employment of mouse and yeast (S. cerevisiae) genetic model systems, biochemical characterization of mitochondrial transcription events and interactions, and in vivo approaches in cultured mammalian cells. Major Ongoing Projects: 1. Nuclear Control of Mitochondrial Gene Expression. This project involves 1) the characterization of human mitochondrial transcription factors and complexes in vivo and in vitro. This involves the study of two dual-function transcription factors/rRNA methyltransferases (h-mtTFB1 and mtTFB2) that play critical roles in mtDNA transcription and replication, mitochondrial ribosome biogenesis, and overall mitochondrial function and biogenesis; 2) charcterization of the functional significance of the direct binding of mitochondrial ribosomal protein L12 to the mitochondrial RNA polymerase (POLRMT); 3) the role of mitochondrial 12S rRNA methylation in maternally inherited deafness (due to the A1555G mtDNA mutation); and 4) generation of mouse gene knock-outs to probe in vivo functions and tissue-specific pathology associated with loss of mtDNA regulation. 2. Mitochondrial Dysfunction and Oxidative Stress in Ataxia-Telangiectasia. We recently discovery that the Ataxia-Telangiectasia Mutated (ATM) checkpoint signaling pathway and its key downstream target ribonucleotide reductase (RNR) are involved in maintaining proper mtDNA copy number and stability in mammalian cells and tissues. Mutations in the ATM kinase cause the multi-faceted disease Ataxia-Telangiectasia (A-T), a key feature of which is oxidative stress in affected tissues. Our preliminary results show that disrupted ATM signaling results in aberrant expression of RNR subunits, improperly regulated mtDNA copy number, increased mtDNA mutagenesis, and ROS accumulation, leading us to hypothesize that mitochondrial dysfunction contributes to the oxidative stress-associated pathology of A-T. This project will dissect mechanistically how disruptions in this pathway affect mitochondrial function in cultured cell and mouse models of the disease, with the goal of identifying potential new therapeutic strategies for A-T pathology. 3. The Role of the Target of Rapamycin (TOR) Pathway in Regulating Mitochondrial Gene Expression, Respiration, and Life Span. Here we are continuing to exploit the budding yeast genetic model system to follow up mechanistically our recent discovery that reduced TOR signaling results in increased mitochondrial translation and respiration, and extension of chronological lifespan. 4. Epigenetic Regulation of the SDHD Gene, Encoding a Subunit of Mitochondrial OXPHOS Complex II. Mutations in the SDHD gene cause hereditary paraganglioma (PGL), a disease characterized by vascularized tumors in the head and neck (commonly in the carotid body, an organ that senses blood oxygen levels). Inheritance of this disease is only observed when mutant SDHD alleles are present on the paternal chromosome, suggesting a unique allele- and tissue-specific form of gene silencing is at play. Defining this imprinting mechanism is the goal of this project. 5. Other Projects. Other projects include 1) the role of the mammalian Pif1 helicase in mtDNA replication and stability; 2) the contribution of mtDNA stability and mitochondrial ROS to intestinal tumorigenesis, and 3) development of methods to transform mammalian mitochondrial with exogenous mtDNA to generate mouse models of mtDNA-based disease pathology.
The Kv2.1 gene encodes a highly conserved delayed rectifier potassium channel that is widely expressed in neurons of the central nervous system. In the bag cell neurons of Aplysia, Kv2.1 channels contribute to the repolarization of action potentials during a prolonged afterdischarge that triggers a series of reproductive behaviors. Partial inactivation of Aplysia Kv2.1 during repetitive firing produces frequency-dependent broadening of action potentials during the afterdischarge. We have now found that, as in mammalian neurons, Kv2.1 channels in bag cell neurons are localized to ring-like clusters in the plasma membrane of the soma and proximal dendrites. Either elevation of cyclic AMP levels or direct electrical stimulation of afterdischarge rapidly enhanced formation of these clusters on the somata of these neurons. In contrast, injection of a 13-amino acid peptide corresponding to a region in the C-terminus that is required for clustering of Kv2.1 channels produced disassociation of the clusters, resulting in a more uniform distribution over the somata. Voltage clamp recordings demonstrated that peptide-induced dissociation of the Kv2.1 clusters is associated with an increase in amplitude of delayed rectifier current and a shift of activation towards more negative potentials. In current clamp recording, injection of the unclustering peptide reduced the width of action potentials and reduced frequency-dependent broadening of action potentials. Our results suggest that rapid redistribution of Kv2.1 channels occurs during physiological changes in neuronal excitability.
http://serendip.brynmawr.edu/exchange/node/1922
The concept of synaptic plasticity is not merely limited to humans, however. In one study done by Sharen McKay, et al., of Yale University, the well known vertebrate enactors associated with synaptic plasticity (neurotrophins) were artificially placed in an invertebrate setting and yet again influenced neuronal growth and plasticity(5). Although invertebrates do not produced neurotrophins, substances with similar effects have been isolated in several invertebrate species. These results suggest that synaptic plasticity is a function that is widely found in many species of life, not merely in a developmental role, but also in the adaptation and modification of adult brains. This article again inspired my theorizing: does the suggestion that "adult plasticity [is] highly conserved across diverse phyla" (5) indicate that the ability of the brain to adapt to learning, memory, and specific experience is an evolutionary advantage?
DNA in mitocondria -- studies mutations of DNA in mitocondria to see if that is causing the diseases
Welcome back to the Lunchtime leaders podcast. Today we will be interviewing Dr. Sharen McKay a _ from Yale University's School of Medicine.
QUICKIE Q
1
2
3
What type of research are you involved in?
What diseases do you think the DNA mutations in the mitochondria are responsible for? Which diseases are you closest to figuring out?
Has the whole sequence of DNA in the mitochondria been mapped? Has the genome mapping you assisted in your research?
We also read some of your research on brain plasticity--and need some advice -- with all of our big tests coming up can you give us some advice on increasing our brain plasticity? LAUGH LAUGH Actually, before the advice can you explain to our listeners what Brain Placity menas.
What made you interested in becoming a scientist?
What are the challenges facing you as a female scientist?
What skills/abilities do you feel students need to have to be successful as 21st century scientists?
Looking at the people currently entering your field, what are their strengths and what are their weaknesses?
There is a lot of discussion in K-12 education about the importance of content knowledge (knowing a lot of "stuff" about math, science, social studies, language arts, etc.) versus the importance of learning skills and students being able to construct their own understanding of material/ideas that are new to them (being able to "learn how to learn"). Considering your job…What are your thoughts regarding how much we should focus on content knowledge versus focusing on students' ability to learn/adapt/grow?
There is also a lot of discussion in education between being successful as an individual and being successful as part of a group or team. Considering the work environment in your field…How important is it for kids to be working in groups in school?
Tell us a little bit about any changes you foresee in scientific research for the next 5-15 years (and beyond). What do you think this means for students currently in high school and for K-12 education in general?
What types of technologies should our students be proficient at using?
What was the best learning/educational experience you have had? Why?
When we're done today, what's the one most important "take-away" message you'd like our teachers and students to hear?
Thank you very much for coming on our show Dr. MckAy. (pause) Before we go, we would like to plug next weeks show. We will be interviewing many of school system's Teacher-of-the-year nominees--live all together for our second from last podcast. Only two more to go before we leave for high school. Our last show will have very, very, special guests-you will not want to miss it.
Pathology is the study and diagnosis of disease through examination of organs, tissues, bodily fluids and whole bodies (Autopsy).
Grad of Wake Forest Neuroscience Program
http://www.yalepath.org/research_labs/shadel/index.htm
Research
In humans, as in most animal cells, genetic information is housed not only in the nucleus, but also in mitochondria (see Figure 1). Mitochondrial DNA (mtDNA) encodes thirteen essential proteins of the oxidative phosphorylation complexes as well as 22 tRNAs and 2 rRNAs required to translate these thirteen mRNAs in the mitochondrial matrix. Mutations in mtDNA cause maternally inherited neuromuscular disorders due to declines in cellular energy metabolism. In addition, mtDNA mutations accumulate in normal aging tissues, certain tumors, and have been implicated in late-onset diseases such a Alzheimer's, Parkinson's, and diabetes, indicating that the pathology of dysfunctional mitochondria is only beginning to be unraveled. The research in my laboratory is directed toward understanding the mechanism of gene expression in human mitochondria and its impact on human aging and disease. The ultimate goal is to understand the full impact of dysfunctional mitochondrial gene expression on human health and use this information to design specific interventions to treat mitochondria-based disease and age-related pathology.Specifically, we focus on nucleus-encoded factors that are imported into the organelle to regulate transcription, translation, replication, and maintenance of mtDNA. We are also concerned with signaling pathways that connect the nuclear and mitochondrial genomes to coordinate gene expession patterns in both compartments. We use multiple approaches to this problem including the employment of mouse and yeast (S. cerevisiae) genetic model systems, biochemical characterization of mitochondrial transcription events and interactions, and in vivo approaches in cultured mammalian cells.
Major Ongoing Projects:
1. Nuclear Control of Mitochondrial Gene Expression. This project involves 1) the characterization of human mitochondrial transcription factors and complexes in vivo and in vitro. This involves the study of two dual-function transcription factors/rRNA methyltransferases (h-mtTFB1 and mtTFB2) that play critical roles in mtDNA transcription and replication, mitochondrial ribosome biogenesis, and overall mitochondrial function and biogenesis; 2) charcterization of the functional significance of the direct binding of mitochondrial ribosomal protein L12 to the mitochondrial RNA polymerase (POLRMT); 3) the role of mitochondrial 12S rRNA methylation in maternally inherited deafness (due to the A1555G mtDNA mutation); and 4) generation of mouse gene knock-outs to probe in vivo functions and tissue-specific pathology associated with loss of mtDNA regulation.
2. Mitochondrial Dysfunction and Oxidative Stress in Ataxia-Telangiectasia. We recently discovery that the Ataxia-Telangiectasia Mutated (ATM) checkpoint signaling pathway and its key downstream target ribonucleotide reductase (RNR) are involved in maintaining proper mtDNA copy number and stability in mammalian cells and tissues. Mutations in the ATM kinase cause the multi-faceted disease Ataxia-Telangiectasia (A-T), a key feature of which is oxidative stress in affected tissues. Our preliminary results show that disrupted ATM signaling results in aberrant expression of RNR subunits, improperly regulated mtDNA copy number, increased mtDNA mutagenesis, and ROS accumulation, leading us to hypothesize that mitochondrial dysfunction contributes to the oxidative stress-associated pathology of A-T. This project will dissect mechanistically how disruptions in this pathway affect mitochondrial function in cultured cell and mouse models of the disease, with the goal of identifying potential new therapeutic strategies for A-T pathology.
3. The Role of the Target of Rapamycin (TOR) Pathway in Regulating Mitochondrial Gene Expression, Respiration, and Life Span. Here we are continuing to exploit the budding yeast genetic model system to follow up mechanistically our recent discovery that reduced TOR signaling results in increased mitochondrial translation and respiration, and extension of chronological lifespan.
4. Epigenetic Regulation of the SDHD Gene, Encoding a Subunit of Mitochondrial OXPHOS Complex II. Mutations in the SDHD gene cause hereditary paraganglioma (PGL), a disease characterized by vascularized tumors in the head and neck (commonly in the carotid body, an organ that senses blood oxygen levels). Inheritance of this disease is only observed when mutant SDHD alleles are present on the paternal chromosome, suggesting a unique allele- and tissue-specific form of gene silencing is at play. Defining this imprinting mechanism is the goal of this project.
5. Other Projects. Other projects include 1) the role of the mammalian Pif1 helicase in mtDNA replication and stability; 2) the contribution of mtDNA stability and mitochondrial ROS to intestinal tumorigenesis, and 3) development of methods to transform mammalian mitochondrial with exogenous mtDNA to generate mouse models of mtDNA-based disease pathology.
LATEST PUBLISHED RESEARCH
Repetitive firing triggers clustering of Kv2.1 potassium channels in aplysia neurons.[My paper] Yalan Zhang, Sharen E McKay, Benoit Bewley, Leonard K Kaczmarek Pharmacology, Yale University, New Haven, CT 06510.The Kv2.1 gene encodes a highly conserved delayed rectifier potassium channel that is widely expressed in neurons of the central nervous system. In the bag cell neurons of Aplysia, Kv2.1 channels contribute to the repolarization of action potentials during a prolonged afterdischarge that triggers a series of reproductive behaviors. Partial inactivation of Aplysia Kv2.1 during repetitive firing produces frequency-dependent broadening of action potentials during the afterdischarge. We have now found that, as in mammalian neurons, Kv2.1 channels in bag cell neurons are localized to ring-like clusters in the plasma membrane of the soma and proximal dendrites. Either elevation of cyclic AMP levels or direct electrical stimulation of afterdischarge rapidly enhanced formation of these clusters on the somata of these neurons. In contrast, injection of a 13-amino acid peptide corresponding to a region in the C-terminus that is required for clustering of Kv2.1 channels produced disassociation of the clusters, resulting in a more uniform distribution over the somata. Voltage clamp recordings demonstrated that peptide-induced dissociation of the Kv2.1 clusters is associated with an increase in amplitude of delayed rectifier current and a shift of activation towards more negative potentials. In current clamp recording, injection of the unclustering peptide reduced the width of action potentials and reduced frequency-dependent broadening of action potentials. Our results suggest that rapid redistribution of Kv2.1 channels occurs during physiological changes in neuronal excitability.
http://serendip.brynmawr.edu/exchange/node/1922
The concept of synaptic plasticity is not merely limited to humans, however. In one study done by Sharen McKay, et al., of Yale University, the well known vertebrate enactors associated with synaptic plasticity (neurotrophins) were artificially placed in an invertebrate setting and yet again influenced neuronal growth and plasticity(5). Although invertebrates do not produced neurotrophins, substances with similar effects have been isolated in several invertebrate species. These results suggest that synaptic plasticity is a function that is widely found in many species of life, not merely in a developmental role, but also in the adaptation and modification of adult brains. This article again inspired my theorizing: does the suggestion that "adult plasticity [is] highly conserved across diverse phyla" (5) indicate that the ability of the brain to adapt to learning, memory, and specific experience is an evolutionary advantage?
DNA in mitocondria -- studies mutations of DNA in mitocondria to see if that is causing the diseases
Welcome back to the Lunchtime leaders podcast. Today we will be interviewing Dr. Sharen McKay a _ from Yale University's School of Medicine.
QUICKIE Q
1
2
3
Thank you very much for coming on our show Dr. MckAy. (pause) Before we go, we would like to plug next weeks show. We will be interviewing many of school system's Teacher-of-the-year nominees--live all together for our second from last podcast. Only two more to go before we leave for high school. Our last show will have very, very, special guests-you will not want to miss it.
Twitter Message
Live Podcast with research scientist from Yale-Need help with questions! Join us at 10:55am http://collaborationnation.wikispaces.com/Steaming+Video+of+Todays+Classhttp://collaborationnation.wikispaces.com/Steaming+Video+of+Todays+Class